Sulpiride-induced hyperprolactinemia in mature female rats: evidence for alterations in the reproductive system, pituitary and ovarian hormones.

BACKGROUND
The prevalence of hyperprolactinemia following administration of conven- tional antipsychotic drugs requires further investigation. The current study is designed to evaluate the effect of sulpiride (SPD)-induced hyperprolactinemia on alterations to ovarian follicular growth, gonadotropins, and ovarian hormones and to analyze the extent of potential problems in mammary glands.


MATERIALS AND METHODS
A total of 40 albino Wistar rats were divided into four groups: control (no treatment), control-sham (0.3 ml olive oil), low dose SPD (20 mg/kg) and high dose SPD (40 mg/kg). All compounds were intraperitoneally (IP) administered for a period of 28 days.


RESULTS
After 28 days, we dissected the rats' ovarian tissues, uterine horns and mammary glands which were sent for histological analyses. We counted the numbers of normal, atretic follicles and corpora lutea (CL). Serum levels of prolactin (PRL), estradiol, progesterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH) were evaluated. SPD-administered animals showed sporadic follicular atresia in different sizes associated with higher numbers of CL on the ovaries. The mammary glands exhibited features of galactorrhea. There was remarkable (p<0.05) elevation in SPD-administered animals' uterine horn endometrium, myometrium and perimetrium thicknesses. The serum levels of PRL and progesterone significantly (p<0.05) increased, while the serum concentration of estradiol, LH and FSH notably (p<0.05) decreased according to the SPD administered dose. No histological and biological changes occurred in control-sham animals. SPD-induced animals had unsuccessful attempts at mating and decreased pregnancy rates.


CONCLUSION
The present findings suggest that SPD-induced disturbances depend on PRL level. In addition, an increased PRL level is largely dependent on the administered doses of SPD.

Introduction compound which selectively blocks postsynaptic dopaminergic neurons. This compound afas an antipsychotic agent to treat schizophrenia. Similar to other medications of the same clas-(1).
PRL is a polypeptide hormone secreted by the lactotroph cells of the anterior pituitary gland. Release of this hormone is pulsatory with approximately 14 pulses per day and it displays significant daily rhythmic levels (2). The primary physiologic role of PRL is to induce lactation and it interacts with other central nervous system (CNS) and peripheral processes. Its secretion is influenced by both stimulatory and inhibitory endogenous and exogenous substances (2, 3). Antipsychotic drugs are known to result in severe elevations in PRL levels (4-6). A remarkable majority of the patients with psychological problems are treated with conventional antipsychotic drugs such as risperidone. These medications have been shown to significantly elevate serum PRL levels (7,8). On the other hand, women of reproductive age are susceptible to medical disorders associated with hyperprolactinemia. It is well established that pathologically increased PRL secretion inhibits follicular estradiol production (9), luteal phase defects, polycystic ovary syndrome (10), and severe follicular atresia (10,11).
In addition to the mentioned disorders, the majority of hyperprolactinemia-induced clinical problems are attributed to the interference of PRL on the hypothalamic-pituitary-gonadal system. PRL suppresses gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus and directly interferes with the pituitary physiologic actions of the gonadotropin luteinizing hormone (LH) and follicle stimulating hormone (FSH) on the gonads (12). On the other hand, follicular growth and granulosa cell physiologic function mainly depend on serum levels of FSH and LH. Therefore dysregulation of ovarian hormones in addition to their impaired correlation with the pituitary gland (feedback mechanisms) will lead to important problems in fertilizing potential (13,14).
Although conventional antipsychotic drugs are known to elevate PRL levels above the upper limit of normal for both men and women, a reliable estimate for the dose-dependent effect of antipsychotic drug-induced follicular atresia is not readily available. Thus, the present study attempts to reconcile the dose-dependent effect and histological structure of uterine horns in rats. Moreover, we have analyzed the mammary glands in order to illustrate hyperprolactinemiainduced histological changes.

Animals and medication administration methods
This experimental study was approved by-Urmia University. In this research, we used 40 mature female Wistar rats, 70 days of age that weighed 160 ± 20 g. The rats were purchased from the Animal Resources Center of the Faculty of Basic Sciences , Urmia University, Urmia, Iran and were acclimatized in an environmentally controlled room (temperaand 12 hours light/12 hours dark schedule). Food and water were given ad libitum. In this study all experiments conducted on animals were in accordance with the Urmia University Guidelines of the Ethical Committee for research on laboratory animals. Following a one week acclimation period, the animals were assigned to four groups (n=10 groups. The control group rats received food and water with no treatment. The control-sham group received daily intraperitoneally (IP) injections of 0.3 ml olive oil for 28 continual days. The test subgroups received either daily 28 continual days.

Histology and morphometry
After 28 days the animals were euthanized by a special CO 2 device and the ovarian, uterine horn and mammary gland specimens were dissected out and fixed in 10% formalin fixative for histological investigations, then embedded in paraffin. Serially prepared sections (5-6 μm) were stained with hematoxylin-eosin (Merck Co, Germany). In the ovarian sections, folli-<100, 101-200, 201-300, 301-400 and >400 μm. Follicular morphology was examined by a microscope with a ×40 objective lens (Olympus, Germany) magnification. Follicles that had a complete layer of flattened granulosa cells, oocytes with cytoplasm, and a normal nucleus were considered normal. Abnormal follicles were classified according to the presence of cytoplasmic damage, a pyknotic nucleus, and combination of damaged nucleus and cytoplasm. Follicular number was estimated by counting the number of follicles in all slides (15). We also counted the corpus luteum (CL) number for each ovary. For histomorphometric analyses, the uterine horn endometrial epithelium, endometrium, myometrium and perimetrium thicknesses were evaluated by a morphometric lens (Olympus, Germany) with a ×40 objective lens. Ultimately the glands' distribution and numbers per one mm 2 were estimated.In addition, we assessed the diameters of the mammary gland lobules and histological features.

Serum sampling and hormonal analyses
Blood samples from corresponding animals were collected directly from the heart. Serum was centrifuged at 3000 g for 5 minutes and subjected to assessments for LH, FSH, progesterone, estrogen (E2) and prolactin levels (PL).

Radioimmunoassay of PRL, LH and FSH in serum
We added a 100 μl aliquots of sera to the tubes which contained 100 μl labeled hormones with rabbit anti-sera in 0.01 M phosphate buffer (pH 7.6). Anti-rat PRL(Cisbio Bioassays, France) the mixture was subsequently centrifuged at 2000×g for 30 minutes and we used a gamma counter to measure the presence of radioactivity in the pellets. The lower limit of sensitivity for the rat PRL assay was 5.2 ng/tube, for LH it was 1.3 ng/tube and for FSH it was 30 ng/tube. Intra-assay coefficient of variance for 10 times PRL (5.9%). Calculated inter-assay coefficient variances for 10 times were 8.98% for FSH, 7.52% for LH and 5.9%for PRL.

Radioimmunoassay of serum estradiol and progesterone
Concentrations of serum estradiol were measured using CIS kits (Cisbio Bioassays, France) according to the methods given by the manufacturer. In brief, serum (300 μl) was extracted with 3 ml ethy lether. The ether layer was evaporated under (N 2 ) gas and the extract resuspended in 300 μl of 0.04 M phosphate tradiol (14000 cpm), each tube was incubated room temperature. Goat anti-rabbit r-globulin (1 ml) was subsequently added and the mixture incubated for 15 minutes at room temperature. After centrifugation, the radioactivity in the resulting pellet was counted. The sensitivity was 1.8pg/tube. In order to evaluate serum level of progesterone we mixed serum (0.1 ml), ethylether (1 ml) and propylene glycol (50 μ1). After the ether was evaporated under N 2 gas, 0.5 ml phosphate buffer and 0.1 ml (20000 cpm) of iodo-progesterone were added to the tube. The mixture was incubated with 0.1 ml anti-serum raised in rabbits for 18 hours at room temperature. Then, 0.1 ml bovine serum gamma globulin and polyethylene glycol were added to the mixture followed by centrifugation for 10 minutes at 2000 g. We measured radioactivitylevels in the resulting pellet. The lower limit of sensitivity was 0.6 ng/ tube (16). The (for 10 times) for estradiol and 4.8% (for 10 times) for progesterone. Calculated inter-assay for 10 times) and progesterone (9.9% for 10 times).

Animal mating
mating and fertilizing ability in different groups, we randomly chose 5 rats from each group. The chosen rats were adjoined with 1 mature normal male rat for 7 days. The vaginal plugs (white coagulum) were checked every day for 7 days and the vaginal smear process was conducted on cases with vaginal plugs in order to clarify the presence or absence of sperm. The day of sperm detection in smears was considered as day 0 of pregnancy and after 21-23 days (pregnancy period in rats) the numbers of rats that were born were counted.

Statistical analysis
perimental data were analyzed using analysis of 's multiple range test (SPSS version 16.00, Chicago, IL, USA). Correlation administered dosewas analyzed on an Indigo-2 O2 Work Station (Silicon Graphics, Mountain View, CA, USA) using Matlab (MathWorks Inc., Natick, MA, USA). P<0.05 was considered to be statisti-

Total body weight gain
We observed no changes in total weight gain of the end of the treatment period. Animals in high ( Fig 1A, B).

Ovarian follicular growth, atresia and corpus luteum (CL)
decreased in comparison to control and controlsham animals. Both left and right ovaries from the control and control-sham groups contained follicles in various stages of development that included primary, secondary and tertiary follicles of different sizes (<100 μm to >400 μm), whereas there was no large antral follicle (>400 μm) in the high animals the cortex of the ovaries (left and right) were covered with small antral atretic follicles (<100-200 μm). Atresia was mostly present in follicles <100 μm and additionally observed in 201-Comparing the rate of normal follicles between the control, control-sham and test groups revealed This reduction was dose-dependent; animals that normal follicles. The highest rate of normal follicles between the test groups was observed in the are depicted in table 2. We observed that animals numbers of CL compared to the control and controlsham groups (Fig 3).

A B C
Mostafapour et al.

Fig 3: Mean number of corpus luteum (CL) per ovary in different groups. Control and control-sham animals exhibited lower numbers of CLs which remained from previous cycles. Sulpiride (SPD)-dosed animals showed higher num-
between SPD-administered groups with control and controlsham animals (n=10 for each group). All data are presented as mean ± SD.

Uterine horn histomorphometry
Comparing the uterine horn endometrial epithelium height (left and right) between all groups showed control and control-sham animals. This impairment epithelium. Simultaneously the endometrial, myometrium and perimetrium thicknesses in both side uterine hornswere remarkably (p<0.05) increased metrial glands per mm 2 of the endometrium were considerably (p<0.05) increased. Animals in control and control-sham groups had remarkably lower numbers of endometrial glands per mm2 of endometrium (Fig 5). The data for histomorphometric analyses are presented in table 3.

Mammary gland morphometry
Light microscopic analyses showed that the lactating alveolus diameter in glands and the distribution of lactiferous ducts remarkably (p<0.05) --analyses showed that simultaneous with remarkable secretory alveoli and ductal development,there were fatty globules observed in the secretory and ' control and control-sham animals had inactive lobules and secretory ducts. The data for histomorphometric analyses are shown in table 4.

Remarkable differences (p<0.05) between low dose SPD group with high dose SPD group. All data are presented as mean ± SD.
contrast, control and control-sham animals showed constant PRL levels. A comparison of LH and FSH showed that serum LH and FSH levels remarkably (p<0.05) decreased in animals that received either administration doses, we observed no statistically the progesterone level remarkably increased in administered group showed the lowest serum level of estradiol and the highest level of progesterone trol-sham groups. The data for hormonal analyses are presented in Figures 7A-C. The data for correlation between PRL, LH and FSH are presented in Figures 8-A and 8-B.

Fertilizing indexes and neonates
Analysis of the fertilizing index in the control, fertilizing index with no neonates. In contrast the control and control-sham animals showed positive fertilizing indexes with 31 and 19 neonates, respectively (Table 5).   It is well established that PRL secretion is regulated via secretion of dopamine in the tubero-inlocated on the surface of the pituitary lactotroph cells. Conventional antipsychotic drugs block the sults in the loss of inhibitory effects of dopamine (17). The results from our biochemical analyses support the mentioned hypothesis; accordingly, --actinemia but also induced hyperprolactinemia is enhanced according to the dose administered.

Discussion
It is well known that PL inhibits follicular estradiol production (9,13,18). In rodents, estrogen is essential for follicular growth, differentiation and for preventing preantral and early antral follicle apoptosis in rats (19). Histological observations have demonstrated remarkably increased atresia (different sizes); these ovaries had higher numbers of CL. On the other hand, according to the dose, the serum level of estrogen decreased with simultaneous increase in proges-Thus, increased PRL levels with a synergistic effect of progesterone resulted in remarkable follicular atresia. Of note, smaller size follicles at the high dose and animals were remarkable for atresia which suggested dependent on the administered dose. These impairments might not only attributeto a higher level of PRL butthey might attribute to CL resistance from previous cycles that in turn lead to severe follicular atresia, which did not allow estradiol secretion to readministered animals proved the above theory.
indicated, the increased level of PRL can largely affect gonadotropins. Our analyses have shown istered groups. In patients who have been treated with antipsychotic-drugs, reduced synthesis and secretion of the GnRH in the hypothalamus is able to decrease enough stimulation for LH and FSH secretion in the pituitary gland (20). Therefore, hypothalamus-pituitary axis which in turn inhibited gonadotropin secretion. Secondly, positive feedback of estradiol through the pituitary gland for LH hormone secretion was eliminated. Thus -ditionally, the decreased estradiol level associated with reduced gonadotropins resulted in CL resist-ance which was delivered from the previous cycle tered animals. Inhibited follicular growth (marked groups proved this theory. In order to evaluate the biological activity of CLs, we investigated the serum levels of progesterone. Observations demonstrated that the serum level of progesterone reconsiderably active. Additionally, because of increased levels of progesterone and absence of an appropriate feedback for androgens and estradiol secretion, in order to start a new cycle (21, 22), follicular growth depression occurred in the ovaries Light microscopic observations demonstrated glandular structure of the endometrium in both considering the luteotrophic effect of PRL and the simultaneous increased progesterone level, we hypothesized that following an increased level of PRL and accomplishing this impairment with higher concentration of progesterone, there was an increase in endometrial thickness and gland distriremarkably higher gland numbers per mm 2 of endometrium.
Mammary gland alveolar development, alveolar epithelium proliferation and/or differentiation largely depend on PRL hormone stimulation (20, 23). Histological analyses showed increased fatty globules in mammary glands and intra-lobular These features have shown that the intensity of galactorrhea majorly depends on the PRL level administered group. From the above mentioned licular growth the ovulation ratio will decrease severely which in turn leads to a negative fertilizproven by our results of the fertilizing indexes in the different groups. Accordingly animals in the indexes and there were no neonates following adjoining the animals with normal male rats (Fig 9).

Fig 9: Regulatory mechanism involved in follicle stimulating hormone (FSH) and luteinizing hormone (LH) secretion and sulpiride (SPD) effect. SPD blocks GnRH secretion which in turn leads to severe reductions in serum levels of FSH and LH.
Conclusion widely used as an antipsychotic drug, the rats serum PRL levels that might be several-fold greater than the upper limit of normal. Adminis--prolactinemia was associated with a disturbance in the levels of essential reproductive hormones, estradiol and progesterone. The PRL-associated disturbances in gonadotropins and reproductive follicular growth and resulted in galactorrhea feaas a PRL-elevating antipsychotic drug, decreased the fertilizing index especially at the higher dose. All the above mentioned results were remarkably